In the Martyrologium Romanum, each day has a heading with the Roman date, and a table that gives the status of the lunar cycle. These are the first things read each day in the Martyrology.

The Roman Date

Each month contains three reference dates: the Kalends, Nones, and Ides. While the Kalends is always the first day of the month; for eight months, Nones and Ides are on the fifth and thirteenth, but in March, May, July, and October, they fall two days later on the seventh and fifteenth.

For example, on July 4th, the Roman date (as styled since Medieval times) is “Quarto Nonas Iulii,” or “Four days before the Nones of July.” While the Nones of July is the 7th, the Roman custom is to count inclusively, so the 4th is considered four days before the 7th.

The day before each reference date is the pridie, so the 6th of July is called: “Pridie Nonas Iulii.”

The Ecclesiastical Moon

The lunar calendar and the phases of the moon are key components in determining the date of Easter, which is set as the Sunday following the first full moon of Spring. On average, there is a new moon (when the moon goes dark) every 29.53 days. In whole numbers, this is figured as each lunar cycle being either 29 or 30 days, depending on the month of the year.

The current Martyrology letter corresponds to the epact, or the difference (in days) between the lunar and solar years. On the table for each day, the numeral beneath the current Martyrology letter corresponds with the age of the moon in its current cycle, from 1 to 29 or 30, with a full moon at 14 or 15.

So, on July 4th 2018, the current Martyrology letter is n, which corresponds to an age of 21 (out of 30), which is said: “Luna vigesima prima.” Which is a moon waning in its last or third quarter phase (about half bright and half dim).

Graciously listen, we beseech thee, O Lord, to the prayers we offer up in commemoration of blessed Athanasius, thy Confessor and Bishop: him thou didst find worthy to render acceptable service to thee; appealed to by his merits, do thou free us from all sin. Through our Lord Jesus Christ, thy Son, who lives and reigns with thee in the unity of the Holy Spirit, one God, forever and ever.

(A suffrage is a short intercessory prayer said to both honor the subject and beg for their heavenly aid. Often said as personal devotions—several one after another. In previous times a number were mandated at the conclusion of Lauds and Vespers, and it matches the traditional form of commemoration of feasts in the Divine Office (Antiphon, Versicle and Prayer).)

Vespers

Sequence for the Feast of Saints Peter & Paul, June 29

Sound, O crowd, the melody in joyful praise,
Joining the words to rhythmic symphony,
May this famous harmony even join the lights of the sky,
Which with golden light illuminate all realms of the world.

Their strong trophies are already blossoming in the kingdom of heaven,
Whose merits dispel the crimes on this shining day.

For one triumphed through the execution on the cross, the other through the sword in the neck, both laurels are shining.
And above the highest stars, famous through their victory, they are prelates in the heavenly court.
From thence, thou, O blessed Peter, who openest [and] closest the great gates of heaven with thy word,
Mildly receive the faithful prayers, dissolving all bonds of sin.

Paul, bring us holy doctrine that illuminateth the hearts of the people,
And carry our minds beyond the stars, as perfectly as God may give.
From thence may come the music of the virtues, fair, with strings and singing,
In that shall be composed the harmony, and that, which is really the original perfect fourth.

Consisting of Virtue and Justice
Of Temperance and Prudence,

With them more than fittingly adorned, let the crowds sing enharmonic canticles to Christ.
May they be joined to our choir, may they give these lights, whom we give more than lyrical songs,
Now everything that is redeemed shall give a solemn Amen.